Powder producing processes and properties

Yegorova S.I.
Magnetic material milling in magnetovibrating layer
The results of the influence of electromagnetic field parameters (induction of constant and variable magnetic fields, induction gradient of variable magnetic field) on milling efficiency of barium ferrite powder and dispersed Nd–Fe–B based material in beater mill in magnetovibrating layer are presented. The modes of electromagnetic action have been chosen to provide maximum crushing of aggregates in magnetovibrating layer. A functional milling time dependence of particle size distribution to allow forecasting the powder grading is proposed.

Key words: mechanical milling, beater mill, magnetovibrating layer, magnetic powders.

Ziganshin I.R., Porozova S.E., Karmanov V.I., Torsunov M.F., Khafizova R.M.
Change of industrial powder characteristics of zirconium dioxide and materials on its basis with mechanochemical activation
The effect of mechanochemical activation on industrial powder of partly yttrium oxide stabilized zirconium dioxide and material properties on its basis have been investigated. Mechanochemical activation in water medium with agar addition is shown to allow production of ultrafine powder with particle size approaching to the nanometer range. The sintering temperature of products, manufactured from it, is higher only by 100 °C than those of nanocrystalline powders. In extending the time activation to ≥10 h, silicon dioxide milling from the lining of the planetary grinding mill has been recorded with IR-spectroscopy. The most strength has been found for the powder activated for 10 h. Increase of silicon dioxide content results in decreasing material strength. Time of 2,5 h is sufficient for effective activation of zirconium dioxide powder without alteration of the powder composition.

Key words: mechanochemical activation, zirconia, doping, strength.

Maltsev I.M.
Electrical rolling of metal powder in roll-electrodes at high-density current
The effect of roll-electrode voltage on the electrical rolling of metal powders has been considered. Formulas were derived for calculation of the voltage during electrical rolling. Values of electrical breakdown for powder materials have been determined experimentally. The optimal voltage values were found during the electrical rolling of widely applicable metal powders.

Key words: electrical rolling, electrical breakdown voltage, ESP method.

Romanov G.N.
Liquid phase sintering of aluminum based powder alloys
Special features of liquid phase sintering of aluminum based powder alloys have been investigated. The found volumetric changes in binary, ternary, and quaternary powder alloys in the course of sintering were shown to be caused by the diffusion nature of interaction of solid and liquid phases. Use of exothermal sintering allows developing the ways of binary powder alloy production. The optimal modes of producing ternary and quaternary powder alloys are found.

Key words: liquid phase sintering, powder body, diffusion, exothermal sintering.

Ratnikov V.I., Prokudina V.K., Belikova A.F., Sachkova N.V.
Titanium powder production from titanium sponge by SHS-hydrogenation and dehydrogenation
Titanium powder production process data from titanium sponge by SHS-hydrogenation and following dehydrogenation are given. The properties of dehydrogenated titanium produced at the optimal conditions have been studied. Dehydrogenated titanium is shown to contain fewer impurities as compared with analogues. The shape of its particles is fused chipped one with nanosized structural elements as cracks, channel, overgrowths, and layers of 100–500 nm in size. Prolonged grinding of initial titanium hydride down to micron sizes does not affect the nanostructured particle surface morphology, results in contamination of final dehydrogenated titanium. The depressiveness of final product varies from sponge dimensions (–10+2 mm) to 20 µm. The results of adjusted calculation of SHS titanium hydride and dehydrogenated titanium production cost are given.

Key words: titanium, sponge, powder, SHS-hydrogenation, dehydrogenation, surface, nanostructured particle, particle size, chemical composition, cost.

Basov V.V., Panov V.S.
Some tendencies in technology and improvement in nuclear fuel quality
The tendencies in improvement of the economic characteristics of nuclear power plants are considered; one of the tendencies is prolongation of the reactor campaign, i.e. a period of fuel placement in the active zone under due increase of its burnup level. In particular, it may be reached by using fuel with burnable absorbers as well as by increase in the quality of fuel pellets produced by powder metallurgy. It is necessary to make the technical requirements to fuel pellets more severe, improve their production process as well as the equipment used for their production. It is noted that the work of improvement of operational factors of fuel pellets (in particular decrease of gas release, decrease in interaction of fuel with cladding) is caused with the production of pellets with burnable absorbers, with production of optimal microstructure (porosity, grain size) of pellets, improvement of their shape, elimination of dust on their surface after smoothing, stabilization of properties by geometrical sizes, density, after-sintering.

Key words: prolongation of the reactor campaign, fuel burnup raise, burnable absorbers, powder metallurgy, compaction, sintering, smoothing, improvement of operational factors, decrease of gas release from pellets, decrease in interaction of fuel with cladding, UO₂ powders, wet and dry granulation, microstructure, porosity, grain size, after-sintering, mechanical strength, improvement of pellet shape, additions, homogeneous, monomodal, and bimodal distribution, pore morphology.

Yartsev D.V., Lakhin A.V., Volfkovich Yu.M., Manukhin A.V., Bogachev E.A., Timofeyev A.N., Sosenkin V.E., Nikolskaya N.F.
Investigation of porous structure of single-layer carbon-ceramic composite material of C–SiC composition
Samples of carbon-ceramic composite material of C–SiC composition have been produced as a result of compaction of silicon carbide deposited from gaseous methylsilane phase, porous compacts produced of fine carbonized carbon fiber-reinforced plastic on the basis of one layer of carbon cloth. Density, porosity, and specific surface of pores have been determined by method of standard porosimetry at every stage of the material production. Based on obtained distributions of specific volume and specific pore surface by their radiuses, the alterations of porous structure of samples are analyzed. Necessity of high-temperature annealing as a composite material production process stage, which results in disappearance of microporosity in composite material, is shown. In addition, the microstructure of composite material under investigation has been studied with SEM.

Key words: C–SiC composite, single-layer composite, carbon cloth, silicon carbide, SiC matrix, chemical vapor infiltration (CVI), methylsilane, method of standard porosimetry, specific surface area, porosity, macro-pores, meso-pores, micro-pores.

Blinkov I.V., Anikin V.N., Sobolev N.A., Mitin V.S., Mitin A.V., Krasnobaev N.N., Volkhonsky A.O., Kashin D.S.
Development of “hybrid” process of wear-resistance coating production based on ion-plasma arc and magnetron spattering
The work is devoted to the development of new “hybrid” method of coating application based on ion-plasma arc and magnetron deposition. The subjects of research were the specimens of the Ti–Al–N system coating on VK-6 alloy carbide blades. The specimens were produced with three different methods: ion-plasma, magnetron, and hybrid ones. The deposition techniques were carried out in vacuum of 1,3∙10^–3 Pa at the substrate temperature of 550–600 °C. VT-5 alloy of the Ti–Al (6 at.%) composition was used as spattered material. The phase and elemental composition of the coatings, their mechanical properties (microhardness and Young module), and adhesion strength have been studied. All the specimens were tested under the continuous cut conditions. The results show the hybrid method produced coating to have a set of positive properties of ion-plasma and magnetron coatings, namely high adhesion strength combined with the uniformity of the composition and structure, whereby its elevated durability can be explained.

Key words: ion-plasma arc spattering, magnetron spattering, adhesion strength, physical-mechanical properties of coatings, durability coefficient.

Koftelev V.T.
On birth of the present-day powder metallurgy

20th year anniversary of the SHS Research-Training Center

Our congratulations to S.S. Ordanyan